I don't think you'll have trouble with 6 Axel locos as much as you'll have trouble with full length passenger cars. At least that's what I've found.
But all the guys who say you MUST have at least 24" radius for a realistic "look" apparently have a bigger basement than I do. it is HARD to achieve much in the way of an interesting layout when you decide your min. will be 24" That's why we wind up with 18"... you can do so much more with the layout that way. Sure 24" would look nicer. But it's a trade off, and I opted for the more interesting layout with tighter curves.
Some six axle diesels will not run well on 18" radius turns and some will. Best thing to do is refer to the manufacturers manual or data sheet. For instance if you look at the broadway limited site for the SD40-2 you will find that the minimum radius is 18"
http://www.broadway-limited.com/catalog/EMD_SD40_2_HO-1775-1.html
If you look at another of their Six axle engines, the AC6000 you'll find that they say the minimum radius is 22" http://www.broadway-limited.com/catalog/GE_AC6000_HO-1771-1.html
I'm sure they would like to sell the AC6000 to those with 18" turns but don't want an unhappy customer with major overhang and de-railments.
Springfield PA
Most anything RTR these days is made to work on 18" radius curves, even if it looks silly doing so. However you will have probklems with long cars and locos if the couplers are mounted to the bodies - on sharp curves they will be offset so far to the outside that they can push trailing cars right off the track.
You mentioned building in a 4x8 space - you cannot use 24" radius cuves on a 4 foot wide layout. The 24" radius is measured fromt he center of the track, so the outside edge is more than 24" in radius, which menas more than 4' in diameter. You can use 22" radius curves on a 4' wide layout though. It's close to the edge though.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Anyone who tells you that six axle diesels won't take an 18" radius curve is either a liar or doesn't know what he's talking about. I run plenty of big six axle jobs on my layout and every curve on it is 18" radius. I run an SD9, SD40, SD40-2's, E6's, E7's, PA's, even a pair of huge SDP40F's. I was even running an AC4400 for a while before I stripped it to rebuild one of the SDP40F's. Sometimes I run my biggest steamer, a 2-10-2.
Dr. Frankendiesel aka Scott Running BearSpace Mouse for president!15 year veteran fire fighterCollector of Apple //e'sRunning Bear EnterprisesHistory Channel Club life member.beatus homo qui invenit sapientiam
Can't be certain of this, but I believe most six axle diesels will track on an 18" radius curve. The real question is will it look right and if you are to run any passenger cars on it will they track. They have a longer overhang and will have trouble coupling to a shorter overhang car. Bob T
I'm definately no expert in this hobby and I have a great deal to learn, but for all you newbies out there like me here's some advise; read, research and plan as much as you can before deciding on a layout or starting a layout. You will save a great deal of time and headaches later on as you can see below
Here's my question:
A few years ago I started building a 4' x 8' layout. I decided on a standard track plan from book, bought the track and turnouts, installed the roadbed and track and found I didn't like the plan. The layout was based on an 18" minimum radius. Now I'm abandoning this layout and designing a new layout based on my prototype (Montana Rail Link), room size and layout and specific industries/scenary I would like to model. What I finding is that my room size and layout is condusive to an 18 minimum radius. Also, I could reuse the turnouts and track I previously purchased. However, I've read that I need a 24" radius to run six axle diesels. Is it still possible to run the six axle diesels on the 18" radius?